The present invention relates broadly to non-linear optical materials, and in particular to the process of making ordered, polymer nonlinear optical materials.
The state of the art of nonlinear optical materials is well represented and alleviated to some degree by the prior art apparatus and approaches which are contained in the following U.S. Pat. Nos.:
U.S. Pat. No. 4,711,532 issued to Choe on Dec. 8, 1987; PA1 U.S. Pat. No. 4,746,199 issued to Nicoud et al on May 24, 1988; PA1 U.S. Pat. No. 4,775,215 issued to Teng et al on Oct. 4, 1988; and PA1 1. liquid crystalline order with the possibility of matching electric field direction to orientation of polymer, PA1 2. fast response (subpicosecond), PA1 3. useful optical window for signal processing, PA1 4. high laser damage threshold, and PA1 5. potential to molecularly engineer properties and process into desired architectures, PA1 1. optical transparency, and PA1 2. optical flatness.
U.S. Pat. No. 4,783,151 issued to Choe on Nov. 8, 1988.
The Choe patent (532) discloses a novel class of diacetylenic monomers and corresponding polydiacetylenic polymers. In the form of an optically transparent medium with a noncentrosymmetric alignment of molecules, the polymer exhibits exceptional second order nonlinear optical susceptibility effects.
The Nicoud et al patent relates to novel paranitroanilin derivatives usable in non-linear optics and electrooptics, as well as to the preparation process for the same. These derivatives are prepared by reacting one or the two pure optical isomers of 2-(hydroxymethyl)-pyrrolidine with a parahalogenonitrobenzene. The optically pure derivatives can be used in optical or optelectronic devices.
The Teng et al patent describes optical devices with an organic nonlinear optical component which is a transparent medium of a wholly aromatic polymer which exhibits a third order nonlinear optical susceptibility .chi..sup.( 3) of at least about 1.times.10-.sup.12 esu. An illustrative embodiment is an ultrafast all-optical gate device with a transparent poly([benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene) optical component which exhibits a third order nonlinear optical susceptibility .chi..sup.( 3) of 10.times.10.sup.-12 esu.
The Choe patent (151) discusses novel polymers which are characterized by a recurring structural unit that contains a pendant quinoid structure and that exhibits nonlinear optical response and are useful in devices such as those used in laser modulation and deflection, frequency conversion, optical communications, integrated circuit fabrication, light valves, and optical switches.
The need for ordered polymers as nonlinear optical materials to provide nonlinear optical effects have emerged at the forefront of research because of their application in optical signal processing, digital optical switching, optical logic, and high speed optical computers. The potential speed (subpicosecond) and large bandwidth capability of optical devices, and their capability for parallel processing of information makes optical signal processing and optical computers very attractive. The requirements of all optical signal processing and optical computing require a combination of properties in materials that favor the development of organic and polymeric materials (4).
The electro-optic properties of conjugated polymeric systems such as the ordered polymers result from electronic (.pi.-electrons) transitions rather than physical orientational motion of the molecules or molecular segments. The electro-optic properties which result from the interaction of light with the electronic transitions in the polymer, are directly related to the third-order nonlinear susceptibility, (.chi..sup.(3)). Material requirements for nonresonant third-order processes are extensive .pi. delocalization, transparency in the spectral region of interest, a high degree of molecular order, and excellent optical quality of the polymeric material such that there is a minimization of scattering by the incident beam.
Ordered polymers potentially offer the unique advantages of:
over existing inorganic materials such as lithium niobate and potassium hydrogen phosphate.
PBT is the subject of recent studies because of its high laser damage threshold and a value of .chi..sup.(3) of 2.7.times.10.sup.-11 esu (more than an order of magnitude higher than that of CS.sub.2.
The environmental stability of PBT along with its excellent mechanical properties make it an excellent candidate for opto-electronic device applications. To be suitable for applications, however, higher values (.about.10.sup.-9 esu) and improved optical quality of films is required. Optical quality will be defined as:
Improved optical quality in ordered polymers can be obtained in a processing technology which minimizes stress birefringence and void formation.
While the above-cited references are instructive, a need remains to provide a nonlinear optical material which possess the above-identified characteristics and properties. The present invention is intended to satisfy that need.